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If Spring can successfully intercept intra class function calls in a #Configuration class, why does it not support it in a regular bean?

I have recently noticed that Spring successfully intercepts intra class function calls in a #Configuration class but not in a regular bean.
A call like this
#Repository
public class CustomerDAO {
#Transactional(value=TxType.REQUIRED)
public void saveCustomer() {
// some DB stuff here...
saveCustomer2();
}
#Transactional(value=TxType.REQUIRES_NEW)
public void saveCustomer2() {
// more DB stuff here
}
}
fails to start a new transaction because while the code of saveCustomer() executes in the CustomerDAO proxy, the code of saveCustomer2() gets executed in the unwrapped CustomerDAO class, as I can see by looking at 'this' in the debugger, and so Spring has no chance to intercept the call to saveCustomer2.
However, in the following example, when transactionManager() calls createDataSource() it is correctly intercepted and calls createDataSource() of the proxy, not of the unwrapped class, as evidenced by looking at 'this' in the debugger.
#Configuration
public class PersistenceJPAConfig {
#Bean
public DriverManagerDataSource createDataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
//dataSource.set ... DB stuff here
return dataSource;
}
#Bean
public PlatformTransactionManager transactionManager( ){
DataSourceTransactionManager transactionManager = new DataSourceTransactionManager(createDataSource());
return transactionManager;
}
}
So my question is, why can Spring correctly intercept the intra class function calls in the second example, but not in the first. Is it using different types of dynamic proxies?
Edit:
From the answers here and other sources I now understand the following:
#Transactional is implemented using Spring AOP, where the proxy pattern is carried out by wrapping/composition of the user class. The AOP proxy is generic enough so that many Aspects can be chained together, and may be a CGLib proxy or a Java Dynamic Proxy.
In the #Configuration class, Spring also uses CGLib to create an enhanced class which inherits from the user #Configuration class, and overrides the user's #Bean functions with ones that do some extra work before calling the user's/super function such as check if this is the first invocation of the function or not. Is this class a proxy? It depends on the definition. You may say that it is a proxy which uses inheritance from the real object instead of wrapping it using composition.
To sum up, from the answers given here I understand these are two entirely different mechanisms. Why these design choices were made is another, open question.

Is it using different types of dynamic proxies?
Almost exactly
Let's figure out what's the difference between #Configuration classes and AOP proxies answering the following questions:
Why self-invoked #Transactional method has no transactional semantics even though Spring is capable of intercepting self-invoked methods?
How #Configuration and AOP are related?
Why self-invoked #Transactional method has no transactional semantics?
Short answer:
This is how AOP made.
Long answer:
Declarative transaction management relies on AOP (for the majority of Spring applications on Spring AOP)
The Spring Framework’s declarative transaction management is made possible with Spring aspect-oriented programming (AOP)
It is proxy-based (§5.8.1. Understanding AOP Proxies)
Spring AOP is proxy-based.
From the same paragraph SimplePojo.java:
public class SimplePojo implements Pojo {
public void foo() {
// this next method invocation is a direct call on the 'this' reference
this.bar();
}
public void bar() {
// some logic...
}
}
And a snippet proxying it:
public class Main {
public static void main(String[] args) {
ProxyFactory factory = new ProxyFactory(new SimplePojo());
factory.addInterface(Pojo.class);
factory.addAdvice(new RetryAdvice());
Pojo pojo = (Pojo) factory.getProxy();
// this is a method call on the proxy!
pojo.foo();
}
}
The key thing to understand here is that the client code inside the main(..) method of the Main class has a reference to the proxy.
This means that method calls on that object reference are calls on the proxy.
As a result, the proxy can delegate to all of the interceptors (advice) that are relevant to that particular method call.
However, once the call has finally reached the target object (the SimplePojo, reference in this case), any method calls that it may make on itself, such as this.bar() or this.foo(), are going to be invoked against the this reference, and not the proxy.
This has important implications. It means that self-invocation is not going to result in the advice associated with a method invocation getting a chance to execute.
(Key parts are emphasized.)
You may think that aop works as follows:
Imagine we have a Foo class which we want to proxy:
Foo.java:
public class Foo {
public int getInt() {
return 42;
}
}
There is nothing special. Just getInt method returning 42
An interceptor:
Interceptor.java:
public interface Interceptor {
Object invoke(InterceptingFoo interceptingFoo);
}
LogInterceptor.java (for demonstration):
public class LogInterceptor implements Interceptor {
#Override
public Object invoke(InterceptingFoo interceptingFoo) {
System.out.println("log. before");
try {
return interceptingFoo.getInt();
} finally {
System.out.println("log. after");
}
}
}
InvokeTargetInterceptor.java:
public class InvokeTargetInterceptor implements Interceptor {
#Override
public Object invoke(InterceptingFoo interceptingFoo) {
try {
System.out.println("Invoking target");
Object targetRetVal = interceptingFoo.method.invoke(interceptingFoo.target);
System.out.println("Target returned " + targetRetVal);
return targetRetVal;
} catch (Throwable t) {
throw new RuntimeException(t);
} finally {
System.out.println("Invoked target");
}
}
}
Finally InterceptingFoo.java:
public class InterceptingFoo extends Foo {
public Foo target;
public List<Interceptor> interceptors = new ArrayList<>();
public int index = 0;
public Method method;
#Override
public int getInt() {
try {
Interceptor interceptor = interceptors.get(index++);
return (Integer) interceptor.invoke(this);
} finally {
index--;
}
}
}
Wiring everything together:
public static void main(String[] args) throws Throwable {
Foo target = new Foo();
InterceptingFoo interceptingFoo = new InterceptingFoo();
interceptingFoo.method = Foo.class.getDeclaredMethod("getInt");
interceptingFoo.target = target;
interceptingFoo.interceptors.add(new LogInterceptor());
interceptingFoo.interceptors.add(new InvokeTargetInterceptor());
interceptingFoo.getInt();
interceptingFoo.getInt();
}
Will print:
log. before
Invoking target
Target returned 42
Invoked target
log. after
log. before
Invoking target
Target returned 42
Invoked target
log. after
Now let's take a look at ReflectiveMethodInvocation.
Here is a part of its proceed method:
Object interceptorOrInterceptionAdvice = this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
++this.currentInterceptorIndex should look familiar now
Here is the target
And there are interceptors
the method
the index
You may try introducing several aspects into your application and see the stack growing at the proceed method when advised method is invoked
Finally everything ends up at MethodProxy.
From its invoke method javadoc:
Invoke the original method, on a different object of the same type.
And as I mentioned previously documentation:
once the call has finally reached the target object any method calls that it may make on itself are going to be invoked against the this reference, and not the proxy
I hope now, more or less, it's clear why.
How #Configuration and AOP are related?
The answer is they are not related.
So Spring here is free to do whatever it wants. Here it is not tied to the proxy AOP semantics.
It enhances such classes using ConfigurationClassEnhancer.
Take a look at:
CALLBACKS
BeanMethodInterceptor
BeanFactoryAwareMethodInterceptor
Returning to the question
If Spring can successfully intercept intra class function calls in a #Configuration class, why does it not support it in a regular bean?
I hope from technical point of view it is clear why.
Now my thoughts from non-technical side:
I think it is not done because Spring AOP is here long enough...
Since Spring Framework 5 the Spring WebFlux framework has been introduced.
Currently Spring Team is working hard towards enhancing reactive programming model
See some notable recent blog posts:
Reactive Transactions with Spring
Spring Data R2DBC 1.0 M2 and Spring Boot starter released
Going Reactive with Spring, Coroutines and Kotlin Flow
More and more features towards less-proxying approach of building Spring applications are introduced. (see this commit for example)
So I think that even though it might be possible to do what you've described it is far from Spring Team's #1 priority for now

Because AOP proxies and #Configuration class serve a different purpose, and are implemented in a significantly different ways (even though both involve using proxies).
Basically, AOP uses composition while #Configuration uses inheritance.
AOP proxies
The way these work is basically that they create proxies that do the relevant advice logic before/after delegating the call to the original (proxied) object. The container registers this proxy instead of the proxied object itself, so all dependencies are set to this proxy and all calls from one bean to another go through this proxy. However, the proxied object itself has no pointer to the proxy (it doesn't know it's proxied, only the proxy has a pointer to the target object). So any calls within that object to other methods don't go through the proxy.
(I'm only adding this here for contrast with #Configuration, since you seem to have correct understanding of this part.)
#Configuration
Now while the objects that you usually apply the AOP proxy to are a standard part of your application, the #Configuration class is different - for one, you probably never intend to create any instances of that class directly yourself. This class truly is just a way to write configuration of the bean container, has no meaning outside Spring and you know that it will be used by Spring in a special way and that it has some special semantics outside of just plain Java code - e.g. that #Bean-annotated methods actually define Spring beans.
Because of this, Spring can do much more radical things to this class without worrying that it will break something in your code (remember, you know that you only provide this class for Spring, and you aren't going to ever create or use its instance directly).
What it actually does is it creates a proxy that's subclass of the #Configuration class. This way, it can intercept invocation of every (non-final non-private) method of the #Configuration class, even within the same object (because the methods are effectively all overriden by the proxy, and Java has all the methods virtual). The proxy does exactly this to redirect any method calls that it recognizes to be (semantically) references to Spring beans to the actual bean instances instead of invoking the superclass method.

read a bit spring source code. I try to answer it.
the point is how spring deal with the #Configurationand #bean.
in the ConfigurationClassPostProcessor which is a BeanFactoryPostProcessor, it will enhance all ConfigurationClasses and creat a Enhancer as a subClass.
this Enhancer register two CALLBACKS(BeanMethodInterceptor,BeanFactoryAwareMethodInterceptor).
you call PersistenceJPAConfig method will go through the CALLBACKS. in BeanMethodInterceptor,it will get bean from spring container.
it may be not clearly. you can see the source code in ConfigurationClassEnhancer.java BeanMethodInterceptor.ConfigurationClassPostProcessor.java enhanceConfigurationClasses

You can't call #Transactional method in same class
It's a limitation of Spring AOP (dynamic objects and cglib).
If you configure Spring to use AspectJ to handle the transactions, your code will work.
The simple and probably best alternative is to refactor your code. For example one class that handles users and one that process each user. Then default transaction handling with Spring AOP will work.
Also #Transactional should be on Service layer and not on #Repository
transactions belong on the Service layer. It's the one that knows about units of work and use cases. It's the right answer if you have several DAOs injected into a Service that need to work together in a single transaction.
So you need to rethink your transaction approach, so your methods can be reuse in a flow including several other DAO operations that are roll-able

Spring uses proxying for method invocation and when you use this... it bypasses that proxy. For #Bean annotations Spring uses reflection to find them.

Java SpringBoot method still #Scheduled under wrong #Profile?

My application.properties file defines the default profile as spring.profiles.active=test and I have a method that I schedule like so:
#Scheduled(initialDelay = 2500, fixedRate = 60 * 1000 * minutesRecheckRate)
#Profile("loop")
public void processingLoop() {
System.out.println(Arrays.toString(env.getActiveProfiles()));
//.. the rest is omitted for brevity.
To my understanding, under these circumstances I should never see this get called while running my unit-tests because I do not change the default profile. This turns out not to be the case, as this is still getting scheduled and I see the output
[test]
in my console despite my best efforts to prevent it. What is happening? Why is this still running even with a different active profile?
UPDATE:
I can't give much more due to the fact this is a work-relevant application, but I'll give what I can.
The class is configured like so:
#Configuration
#EnableScheduling
public class BatchConfiguration {
The unit tests are all annotated like this:
#SpringApplicationConfiguration(classes = SpringBatchJsontestApplication.class)
public class SpringBatchJsontestApplicationTests extends AbstractTestNGSpringContextTests {
The main application class is this:
#SpringBootApplication
public class SpringBatchJsontestApplication {
None of them change anything else. There is no context.xml file, this is a SpringBoot application so everything is annotations only.
This is the end result that works very well for me
#Profile("test")
#Bean(name = TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME)
#Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public ScheduledAnnotationBeanPostProcessor scheduleBeanProcessorOverride() {
logger.info("Test Profile is active, overriding ScheduledAnnotationBeanPostProcessor to prevent annotations from running during tests.");
return new ScheduledAnnotationBeanPostProcessor() {
#Override
protected void processScheduled(Scheduled scheduled, Method method, Object bean) {
logger.info(String.format("Preventing scheduling for %s, %s, %s", scheduled, method, bean.getClass().getCanonicalName()));
}
};
}
Here is the POM configuration to trigger the testing profile, so I no longer have to do so explicitly in my application.properties.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.19</version>
<configuration>
<systemPropertyVariables>
<spring.profiles.active>test</spring.profiles.active>
</systemPropertyVariables>
</configuration>
</plugin>

The #Profile annotation doesn't do anything for a regular method, nor a method annotated with #Scheduled. The javadoc states
The #Profile annotation may be used in any of the following ways:
as a type-level annotation on any class directly or indirectly annotated with #Component, including #Configuration classes
as a meta-annotation, for the purpose of composing custom stereotype annotations
as a method-level annotation on any #Bean method
The last case, in bold, is the only use of #Profile on a method.
If you want to enable the #Scheduled behavior under a specific profile, annotate the bean (definition) that contains it.

Intercept private annotated method with AOP

I have a custom annotation:
#Target({ElementType.METHOD, ElementType.TYPE})
#Retention(RetentionPolicy.RUNTIME)
public #interface FeatureSwitch {
String featureName();
}
I intercept this with the below aspect and use it to check if a feature is on or off. If the feature is off, then I throw an exception.
Aspect:
#Aspect
public class FeatureSwitchAspect {
private final FeatureSwitchConfigurationApi featureSwitchConfigurationApi;
public FeatureSwitchAspect(final FeatureSwitchConfigurationApi featureSwitchConfigurationApi) {
this.featureSwitchConfigurationApi = featureSwitchConfigurationApi;
}
#Before("#annotation(featureSwitch)")
public void checkFeatureSwitch(final FeatureSwitch featureSwitch) {
final String featureName = featureSwitch.featureName();
Boolean featSwitch = featureSwitchConfigurationApi.isFeatureActive(featureName);
if (!featSwitch) {
throw new FeatureSwitchOffException();
}
}
}
The problem I am having is that the behaviour seems inconsistent. This seems to do as expected when I call a method from a different class, but if I make a call to an annotated private method, no interception occurs. Have I got it configured incorrectly? Any suggestions would be appreciated.

Method calls from within classes will not work with proxy-based AOP.
Since you are using the keyword this (which is a pointer to your original object and not the proxy objects that is wrapping it), you will be calling the wrapped method directly - thus bypassing the code added as a result of your AOP.

You have tagged your question by java and aop, not by spring or spring-aop. So I assume that you are not limited to proxy-based Spring AOP but can use a full-fledged AOP solution like AspectJ (possible even within Spring or application servers). If so, there is a solution:
Use a privileged aspect. Caveat: This is supported in native AspectJ syntax, but not in #AspectJ syntax.

Rest + Spring AOP + interface doesn't inject

I have a Spring AOP aspect used for logging, where a method can be included for logging by adding an annotation to it, like this:
#AspectLogging("do something")
public void doSomething() {
...
}
I've been using this on Spring beans and it's been working just fine. Now, I wanted to use it on a REST-service, but I ran into some problems. So, I have:
#Path("/path")
#Service
public class MyRestService {
#Inject
private Something something;
#GET
#AspectLogging("get some stuff")
public Response getSomeStuff() {
...
}
}
and this setup works just fine. The Rest-service that I'm trying to add the logging to now has an interface, and somehow that messes stuff up. As soon as I add the #AspectLogging annotation to one of the methods, no dependencies are injected in the bean, and also, the aspect is newer called!
I've tried adding an interface to the REST-service that works, and it gets the same error.
How can having an interface lead to this type of problems? The aspect-logger works on classes with interfaces elsewhere, seems it's only a problem when it's a REST-service..

Ref the below Spring documentation (para 2) -
To enable AspectJ annotation support in the Spring IoC container, you
only have to define an empty XML element aop:aspectj-autoproxy in your
bean configuration file. Then, Spring will automatically create
proxies for any of your beans that are matched by your AspectJ
aspects.
For cases in which interfaces are not available or not used in an
application’s design, it’s possible to create proxies by relying on
CGLIB. To enable CGLIB, you need to set the attribute
proxy-targetclass= true in aop:aspectj-autoproxy.
In case your class implements an interface, a JDK dynamic proxy will be used. However if your class does not implement any interfaces then a CGLIB proxy will be created. You can achieve this #EnableAspectJAutoProxy. Here is the sample
#Configuration
#EnableAspectJAutoProxy
public class AppConfig {
#Bean
public LoggingAspect logingAspect(){
return new LoggingAspect();
}
}
#Component
#Aspect
public class LoggingAspect {
...
...
}

In my opinion what you are actually trying to do is to add spring annotations to a class maintained by jersey. In the result you are receiving a proxy of proxy of proxy of somethng. I do not think so this is a good idea and this will work without any problems. I had a similar issue when I tried to implement bean based validation. For some reasons when there were #PahtParam and #Valid annotations in the same place validation annotations were not visible. My advice is to move your logging to a #Service layer instead of #Controller.

Perf4j #profiled annotation for private method

I have added #Profiled annotation for public and private method. I can see the timing logs for public methods. But there is no timing logs for private methods.
I did the configurations correctly.
#Profiled
public BigInteger nextPrime() {
currentPrime = currentPrime.nextProbablePrime();
return currentPrime;
}
#Profiled
private void test()
{
try{
Thread.sleep(100);
}catch(Exception e)
{
e.printStackTrace();
}
}
Is #profiled annotation only applicable for only public methods?

Most likely you have configured perf4j with Spring AOP and since Spring AOP proxies are not invoked when a method is called from inside the same class (as in your case with the test method), no performance statistics will be recorded.
Check out this blog post which explains Spring AOP pitfalls
One solution to your problem would be to use AspectJ with perf4j, since AspectJ can handle this type of situation

Yes. It is limitation of the Spring AOP:
When using proxies, you should apply the you annotations only to
methods with public visibility. If you do annotate protected, private
or package-visible methods with these annotations, no error is raised,
but the annotated method does not exhibit the configured caching
settings. Consider the use of AspectJ (see below) if you need to
annotate non-public methods as it changes the bytecode itself.”